Chefaa.
Clean architecture Concepts with MVVM and RxSwift
Installation
Dependencies in this project are provided via Cocoapods. Please install all dependecies with
pod install
High level overview
Domain
The Domain is basically what is Chefaa's App about and what it can do (Entities, UseCase etc.) It does not depend on UIKit or any persistence framework, and it doesn't have implementations apart from entities
Platform
The Platform is a concrete implementation of the Domain in a specific platform like iOS. It does hide all implementation details. For example Database implementation whether it is CoreData, Realm, SQLite etc.
Application
Application is responsible for delivering information to the user and handling user input. It can be implemented with any delivery pattern e.g (MVVM, MVC, MVP). This is the place for your UIViews and UIViewControllers. As you will see from the example app, ViewControllers are completely independent of the Platform. The only responsibility of a view controller is to "bind" the UI to the Domain to make things happen. In fact, in the current example we are using the same view controller for Realm and CoreData.
Detail overview
To enforce modularity, Domain, Platform and Application are separate targets in the App, which allows us to take advantage of the internal access layer in Swift to prevent exposing of types that we don't want to expose.
Domain
Entities are implemented as Swift value types
public struct Item {
public let id: Int
public let title: String
public let images: [String]
public let price: Double
}UseCases are protocols which do one specific thing:
public protocol AdvertisementsUseCase {
func homeComponents() -> Observable<HomeComponentsTypeAlias>
}
UseCaseProvider is a service locator. In the current app, it helps to hide the concrete implementation of use cases.
Platform
The Platform also contains concrete implementations of your use cases, repositories or any services that are defined in the Domain.
final class AdvertisementsUseCase: Domain.AdvertisementsUseCase {
private let network: HomeNetwork
init(network: HomeNetwork) {
self.network = network
}
func homeComponents() -> Observable<(sliders: [SliderAdvertisement], subCategories: [SubCategory], brands: [Brand], items: [Item], landingPages: [LandingPage])> {
let homeComponents = network.fetchHome().flatMap { home -> Observable<(sliders: [SliderAdvertisement], subCategories: [SubCategory], brands: [Brand], items: [Item], landingPages: [LandingPage])> in
guard let brands = home.data?.brands,
let sliders = home.data?.slider,
let subCategories = home.data?.subCategories,
let items = home.data?.bestselling,
let landingPages = home.data?.landingPages else {
return Observable.of((sliders: [], subCategories: [], brands: [], items: [], landingPages: []))
}
return Observable.of((sliders: sliders, subCategories: subCategories, brands: brands, items: items, landingPages: landingPages))
}
return homeComponents
}
}As you can see, concrete implementations are internal, because we don't want to expose our dependecies. The only thing that is exposed in the current app from the Platform is a concrete implementation of the UseCaseProvider.
public final class UseCaseProvider: Domain.UseCaseProvider {
private let networkProvider: NetworkProvider
public init() {
networkProvider = NetworkProvider()
}
public func makeAdvertisementsUseCase() -> Domain.AdvertisementsUseCase {
return AdvertisementsUseCase(network: networkProvider.makeHomeNetwork())
}
}Application
In the current example, Application is implemented with the MVVM pattern and heavy use of RxSwift, which makes binding very easy.
Where the ViewModel performs pure transformation of a user Input to the Output
protocol ViewModelType {
associatedtype Input
associatedtype Output
func transform(input: Input) -> Output
}final class HomeViewModel: ViewModelType {
// MARK: - ViewModel Inputs
struct Input {
let trigger: Driver<Void>
}
// MARK: - ViewModel Outputs
struct Output {
let fetching: Driver<Bool>
let homeAds: Driver<HomeComponentsViewModelsTypeAlias>
let error: Driver<Error>
}
// MARK: - Properties
private let useCase: AdvertisementsUseCase
private let navigator: HomeNavigator
// MARK: - Init
init(useCase: AdvertisementsUseCase, navigator: HomeNavigator) {
self.useCase = useCase
self.navigator = navigator
}
// MARK: - ViewModel Transformation
func transform(input: Input) -> Output {
....
}
}
A ViewModel can be injected into a ViewController via property injection or initializer. In the current app, this is done by Navigator.
protocol HomeNavigator {
func toHome()
}
class DefaultHomeNavigator: HomeNavigator {
// MARK: - Properties
private let storyBoard: UIStoryboard
private let navigationController: UINavigationController
private let services: UseCaseProvider
// MARK: - Init
init(services: UseCaseProvider,
navigationController: UINavigationController,
storyBoard: UIStoryboard) {
self.services = services
self.navigationController = navigationController
self.storyBoard = storyBoard
}
// MARK: - HomeNavigator Functions
func toHome() {
let viewController = storyBoard.instantiateViewController(ofType: HomeViewController.self)
viewController.viewModel = HomeViewModel(
useCase: services.makeAdvertisementsUseCase(),
navigator: self
)
navigationController.pushViewController(viewController, animated: true)
}
}
class HomeViewController: UIViewController {
private let disposeBag = DisposeBag()
var viewModel: HomeViewModel!
...
}Modularization
The corner stone of Clean Architecture is modularization, as you can hide implementation detail under internal access layer. Further read of this topic here
Links
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